RE: Update Existing Contact from a lead
Hi Lisa,
In this scenario, when Qualify Lead, you don't need to create a new Contact, but only update Existing Contact, right?
If so, we will create a workflow.
Go to Advanced Settings > Processes, new a workflow for Lead.

Check Record status changes. Select Scope to Organization.

Add a step - Check Condition.
If Lead:Status equals [Qualified] AND Lead:Parent Contact for lead contains data

Then add a step - Update Record.
Update Parent Contact for lead, use Lead's fields dynamics value to update the Contact's fields.

Finally activate the workflow.